Optical helium lines reveal accretion geometry on super Jupiter Delorme 1 (AB)b

Star system: 2MASS J0103-5515 A | Distance from the Sun: 154 light years

Delorme 1 (AB)b is a young, massive planet—about 13 times the mass of Jupiter—orbiting a binary star at a wide distance. Using high-resolution optical spectroscopy, scientists detected seven helium emission lines from the planet, which show significant variability and asymmetric profiles. The lines have both narrow and broad components, with the broad part redshifted by about 15 km/s, indicating complex gas motions.

The analysis suggests that the narrow helium emission comes from the post-shock region near the planet's surface, where material falls onto the planet and heats up. The broad, redshifted component likely originates closer to the shock front, where gas is still moving rapidly. The measured accretion luminosity and mass accretion rate are consistent with, but slightly higher than, estimates from ultraviolet observations. These findings show that Delorme 1 (AB)b accretes material in a way similar to young stars, but with narrower line widths due to its lower mass.

This study demonstrates that helium emission lines are powerful tools for probing accretion processes in planetary-mass objects and can reveal details about how gas falls onto forming planets.

Key findings
- Seven optical helium lines detected from Delorme 1 (AB)b
- Emission lines show narrow and broad, redshifted components
- Narrow component forms near the planet's surface in the post-shock region
- Broad component originates closer to the shock front
- Accretion geometry is similar to that of young stars but with narrower lines

Scientific study

ExoplaNeT accRetion mOnitoring sPectroscopic surveY (ENTROPY) III. Optical He I line profiles of the accreting super Jupiter Delorme 1 (AB)b (external link)